Systems are able to reduce or remove slowly-varying drift errors, such as heading errors, rate of rotation errors, and direction of travel errors, to correct the measurements from tracking devices. The systems may be used to remove the slow varying drift errors for gyroscopic tracking device sensors, or other types of sensors used for determining heading, rates of rotation, direction of travel, or position. The systems may be employed in personal dead reckoning systems, or other personnel tracking device, as well as in vehicle tracking devices. The system uses heuristic assumptions to correct for these drift errors, via a feedback loop control having an accumulator responsive to changes in output signals. The accumulator is able to produce a signal that over time compensates for the inherent drift errors on those output signals.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made in part with government support under Contract No. DE FG52 2004NA25587 awarded by the U.S. Department of Energy and in part by the Ground Robotics Reliability Center (GRRC) at the University of Michigan, with funding from government contract DoD-DoAW56H2V-04-2-0001 through the Joint Center for Robotics. The government has certain rights in the invention.